Magnetic Loop Antennas
- Al Lúgaro - KP3A
- 11 ago 2016
- 2 Min. de lectura
Magnetic Loop Antennas are an explained mystery, however it never ceases to amaze me on their performance. For the past couple of years I have been building and playing with Small transmitting Loops (STL's) and fun its an understatement. I first saw an old poster of a German soldier WWII era on skies and with a magnetic loop antenna on his backpack. I was told they were forward observers during the war and transmitted theit findings on CW on the HF spectrum. Some years ago I did some work at a receiving station that had over 50 of them well aligned , but they were not in use at the time. They are very easy to build and the performance for indoors or restricted areas is unequaled. The main loop needs to be less that 1/4 of a wave at a given frequency and the small loop, the feeder is one fifth (1/5th) of the size of the main loop. The signal is transferred from one loop to the other is purely magnetic, hence much of the noise from surrounding and the band stays behind. The most important part is the tuning capacitor, they can be found around, but you might no find the value you need, they are also available on ebay and other sites. There is a big variety of the capacitors, some are open air, some are vacuum sealed either way you need the right capacitance to be able to tune it. There are several websites that contain information with details on how to build and use this antenna. This past June (2016) I worked ZL2IO using 4 watts and a 36" in diameter loop from the beach near my home. Have fun they are worth the try, I carry on of mine on the back seat of my car and I can have up and running in 5 minutes on top of a camera tripod. Best 73 KP3A
In use above a two turn STL on 40 mtrs at my sunset time, Radio is an SDR IQ by RF Space.